Boy, if that ain't the truth!
Without side rails or those guide posts on the original MacGregor trailer, loading the boat centered on the trailer is almost impossible. Done by yourself, it becomes a matter of luck by repeatly pulling the trailer out of the water until it centers. With any wind, you can forget ever getting the boat center just right! Just a few more bucks invested in the MacGregor trailer design would have saved a lot of ill will toward the designer.